Mississippi Republican Gregg Harper announced Thursday that he would not seek reelection in 2018. Harper, who is in his 5th term, represents the state's 3rd district, a safe Republican area that Donald Trump won by nearly 25 points in 2016. The district crosses the state, from the border with Louisiana to that with Alabama. It includes part of the Jackson area, as well as Meridian.

Related: Full list of House Retirements

Separately, Ohio Republican Pat Tiberi, who announced this past October that he would leave Congress by the end of January, has set January 15th as his departure date. Gov. John Kasich, who represented the 12th district prior to Tiberi (both of them served nine terms) will set the date for a special election. Donald Trump won this district by about 11% in 2016 and it likely will remain in Republican hands.

Pennsylvania Republican Rep. Bill Shuster announced Tuesday he will not seek reelection in 2018. Shuster is in his 9th term, and chairs the House Transportation and Infrastructure Committee.

Shuster represents Pennsylvania's 9th district, which covers a large part of the south-central part of the state. The seat is safely Republican. Donald Trump won the district by over 42 points in 2016, his largest margin anywhere in the state. 

Shuster becomes the third Pennsylvania U.S. House member - all Republicans - to pass on the 2018 race. Rep. Charlie Dent (PA-15) is also retiring, while Rep. Lou Barletta (PA-11) is running for U.S. Senate. 

This is the first House retirement announcement of 2018. There are now 41 members on the list of departures, including 27 Republicans and 14 Democrats. One of the Republicans, Ohio's Pat Tiberi, is expected to leave Congress this month.

Utah Republican Senator Orrin Hatch announced he will retire at the end of this year. The departure opens the door to a likely run by Mitt Romney, the 2012 Republican presidential nominee and former Massachusetts governor. Romney reportedly indicated to associates last year that he would enter the race if Hatch chose not to run.

Now in his 7th term, Hatch is the longest-serving Republican in the Senate. He joined in early 1977 after winning in 1976. Only Vermont's Patrick Leahy, who entered the Senate in 1975, has served longer. Leahy was elected to an 8th term in 2016.

Romney would be the prohibitive favorite to win should he choose to run.

Two new Senators will be seated Wednesday as the 2nd session of the 115th Congress convenes. Alabama Democrat Doug Jones will replace Republican Sen. Luther Strange, while Democratic Minnesota Lt. Gov. Tina Smith will fill the seat being vacated by fellow Democrat Sen. Al Franken.

Jones defeated Republican Roy Moore in a special election on December 12th. He is the first Democrat to win a Senate election in Alabama since 1992, when Richard Shelby was reelected to a 2nd term. Shelby would become a Republican two years later. Now in his 6th term, Shelby remains the state's senior Senator. Jones will serve the remainder of the term. The seat is up again in 2020.

Smith was appointed by Minnesota Gov. Mark Dayton to replace Franken. She is expected to face the voters in a special election this November. The winner there will complete the remainder of Franken's term. This seat is also up again in 2020.

The Democratic gain in Alabama will bring the Senate to 51-49 Republican. Democrats will need to pick up two seats to gain control in 2018.

Minnesota Sen. Al Franken has set January 2, 2018 as his resignation date. His replacement, Lt. Gov. Tina Smith, will be sworn in the following day. She was appointed to the position by Minnesota Gov. Mark Dayton after Franken announced his intention to resign earlier this month. 

When Smith is seated, Minnesota will become just the 6th state to ever have two female Senators serving simultaneously. The other five include California, New Hampshire, Washington, Kansas and Maine. The first three states in that list currently have two women in the Senate.

Smith's appointment is temporary. Minnesota will hold a special election coinciding with the midterm elections next November. The winner will serve the final two years of Franken's term. That seat's next regularly scheduled election is in 2020.

Minnesota's other Senator, Amy Klobuchar, is also up for reelection in 2018. According to an analysis by Sabato's Crystal Ball, this will be the 55th time since 1913 that a state has had a 'double-barrel' Senate election. The analysis shows that in the vast majority of cases, the same party wins both elections. In fact, this has been the case 100% of the time since 1966. 

Use our Senate Interactive Map, now updated for Alabama and Minnesota, to create and share your own 2018 Senate election forecast.

The Census Bureau released its annual national and state population estimates on Wednesday, noting that Idaho was the nation's fastest growing state for the year ending July 1, 2017. Election Data Services has extrapolated population growth from 2010-17 through to 2020, when the next Census will take place.

Among other things, the Census will determine how the 435 congressional districts will be reallocated next decade. This, in turn will determine changes to the electoral map. Each state receives an allocation of electoral votes equal to the number of congressional districts it has plus two for its Senators. 

At this point, Texas and Florida look to be the big winners, gaining 3 and 2 electoral votes, respectively. Arizona, Colorado, North Carolina and Oregon will gain one each. As the number of electoral votes is fixed, these 9 increased votes must come from somewhere else. The current projection is that Alabama, Illinois, Michigan, Minnesota, New York, Ohio, Pennsylvania, Rhode Island and West Virginia are on track to lose one each. This projection is virtually unchanged from late 2016. The only difference is that Illinois, as opposed to Texas, would be allocated the final congressional district.

Of course, much can change between now and 2020. For example, hurricane Maria devastated Puerto Rico this summer - after the July 1 estimate date - leading to an outward migration of those residents to Florida. It is unknown how many of those will return to the island when life gets back to normal there.

We've created interactive maps of the last five presidential elections using the projected 2024 map. There's little change from 2016, where Donald Trump would win two more electoral votes with the 2024 map. However, looking back to 2000, George Bush would have won 19 more electoral votes, giving him a wider 290-248 victory over Al Gore. That said, Florida would still have made the difference. The Sunshine State is projected to have 31 electoral votes in 2024, vs. 25 in 2000.

The U.S. House of Representatives passed the tax reform bill Tuesday. The measure will now head to the U.S. Senate. If approved, it will then forwarded to President Trump for his signature. 

227 Republicans supported the measure, while 12 opposed. 191 Democrats voted against the measure, while 2 did not vote. Of the 12 Republicans voting no, 11 are from California, New Jersey, or New York, all states with areas of expensive real estate, as well as a high income and/or property tax burden. The bill places limits on the amount of these taxes that can be deducted, as well a reduced mortgage interest deduction.

Curious how your representative voted? You can check here. That page also shows how each representative in a competitive 2018 district voted. Click or tap a state to see how each member of that state's delegation voted.

Related: Will your taxes go up or down? Use this interactive calculator to find out.

Nevada Rep. Ruben Kihuen, who is facing multiple sexual harassment claims, has announced he will not seek reelection to his seat in 2018. Kihuen, who former Sen. Harry Reid once called "a rising star in Nevada and the Democratic Party", unseated Republican Cresent Hardy in 2016 to become Nevada's first Latino congressman.

Nevada's 4th congressional district encompasses North Las Vegas and a large portion of rural central Nevada. The district was created after the 2010 Census, as the state added a congressional district due to rapid population growth. As recently as 1980, there was one at-large representative for the entire state. Kihuen is the 3rd person to represent the district, each of whom will have served only one term.

Hillary Clinton won the district by 5 points over Donald Trump in 2016. The seat is currently rated as 'Leans Democrat' for 2018.

Kihuen becomes the 40th House member, and 2nd from Nevada, to announce they aren't seeking reelection in 2018. Kihuen's colleague, Rep. Jacky Rosen, also in her first term, is attempting to unseat Sen. Dean Heller.

The 2018 Senate Interactive Map has been updated to reflect the 34 seats to be contested on November 6, 2018. This includes a special election in Minnesota, where Gov. Mark Dayton has appointed Lt. Gov. Tina Smith to take over when Sen. Al Franken departs. The recently completed Alabama special election has been removed. (These two special election seats will again be contested in 2020, while the 33 remaining 2018 elections are for six-year terms through 2024). 

Once Alabama Democrat Doug Jones is seated, the Senate will consist of 51 Republicans, 49 Democrats*. That means Democrats will need to gain two seats in 2018 to take control in 2019, as Vice-President Pence will break any ties in a 50-50 Senate in favor of the Republicans. The win in Alabama gives them an opening to accomplish that, but it is still an uphill climb due to the particular seats up in this cycle.

The following maps are all interactive, and all are based on the Senate after Mr. Jones is sworn-in. Click on any of them to create and share your own 2018 Senate forecast

Blank Map: The 34 Senate seats to be contested in 2018. Only 8 of 51 Republican seats are up this cycle, the remaining 43 split between 2020 and 2022. 

Current Party: The 34 seats are filled in with the incumbent party. The Senate would remain 51-49 Republican if no seats flipped in the 2018 midterms.

Safe Seats: The 16 seats rated 'safe' by all three of Sabato's Crystal Ball, The Cook Political Report, and Inside Elections. The remaining 18 seats, with the tan shading, are or could become competitive in the eyes of one or more of these pundits. The GOP need only win 3 of these 18 to maintain control.  

How Democrats Gain Control: The most likely path is for Democrats to defend all the seats they hold (medium blue) and win two Republican-held seats. Arizona and Nevada (light blue) are considered toss-ups by all three pundits and are the most likely route. Absent both of those, Tennessee and Texas (medium red) would be the only other prospects, although Democrats face much greater odds.    

How Republicans Keep Control: This remains the most likely outcome of the 2018 midterms. Any 'Democrats Gain Control' scenario, like the one above, means the party must win 28 of 34 elections. That's no easy feat even if everything goes perfectly for the blue team. However, as we've seen in recent weeks, long political careers can be derailed in a manner of days.

For example, the seat held by Al Franken may well be competitive in 2018; it was previously considered safe Democratic territory. In addition, Democrats must win five states that Donald Trump won in 2016 by 18% or more. In this map, we show those states, plus Republican-held Arizona and Nevada, as in-play (tan). Assuming no other surprises, a Republican win in just one of those 7 states and the GOP keeps control.

The Associated Press has called the Alabama special election for Doug Jones. 

Once Jones is seated, Republicans will hold 51 seats vs. 49 for Democrats.