The battle for control of Congress heats up in coming weeks, as a new House member will be elected in Pennsylvania and primary elections will start in parts of the country.
But this week, the gun control debate and other issues that will help to define November's midterm congressional elections will play out in Washington and around the country. Republicans are trying to hold on to majorities in both chambers of Congress, while Democrats hope to leverage opposition to President Donald Trump to at least win enough seats to take control of the House.
Here are some of the storylines to watch this week for the midterm elections:
Gun control: Congress returns to Washington this week amid a raging national debate about gun restrictions. The shooting massacre of 17 people at a Florida high school on Feb. 14 started fresh momentum for at least modest action to tighten gun control laws.
A string of recent national polls has shown strong support for tougher gun rules. Three separate polls released in the past week from Quinnipiac, CNN and CBS found about two-thirds of either voters or Americans overall back more gun control.
The extent of the gun control debate's potential effect on November's races is still unclear. However, the Quinnipiac poll could give some clues:
President Donald Trump and Republican Senate leaders want to pass a bill to improve the existing federal background check system. While the House already passed legislation to strengthen background checks, it did so in tandem with a bill loosening concealed carry laws. As of now, it appears some House conservatives could insist on approving the concealed carry provision along with the background check measure.
The debate will be particularly important in the race for a Senate seat in Florida, a state Trump won in 2016. Republican Gov. Rick Scott is expected to challenge incumbent Democratic Sen. Bill Nelson later this year. Scott has started to take narrow steps to restrict access to guns, and Nelson has already positioned himself as tougher on gun control.
Scott and Republican leaders in Florida's legislature have put forward varying proposals to tighten gun rules, according to Politico, including increasing the minimum age to buy any gun to 21, setting a three-day waiting period for assault-style rifles and banning bump stocks, which effectively allow semi-automatic rifles to fire like automatic weapons. The influential National Rifle Association opposes pieces of Scott's plan, and it is unclear whether the organization can leverage GOP lawmakers to sink the proposals.
On Friday, Nelson argued that Scott's plans do not go nearly far enough to address the problem, according to the Orlando Sentinel. The senator contended that Scott did the "bare minimum."
Dianne Feinstein: Over the weekend, the California Democratic Party declined to endorse 84-year-old Sen. Dianne Feinstein. Party activists threw more support to her challenger, 51-year-old state Senate leader Kevin de Leon. Neither candidate reached the 60 percent threshold needed to secure the party's endorsement.
While the result does not yet spell doom for Feinstein statewide, it marks the first time she has not received the party's backing since she first won a Senate campaign in 1994, according to The Associated Press. It shows some momentum with de Leon, who has cast himself as a fresh, progressive candidate. He has criticized Feinstein for not taking strong enough opposition to Trump.
Feinstein and de Leon will first face off in a primary in June. Because of the way the state's elections work, the pair will likely also be on the ballot in the general election in November.
Arizona special election primary: On Tuesday, a special primary election will take place for Arizona's 8th congressional district. Republican Rep. Trent Franks stepped down in December.
At least 10 Republicans and two Democrats aim to win their party's nomination for the April 24 special election. At this point, the GOP candidate who emerges may prove more important. The handicapper Cook Political Report rates the seat as "solid" Republican.
The leading GOP candidates include state Sens. Debbie Lesko and Steve Montenegro, as well as Phil Lovas, a former state House member. A poll released last month showed Lesko and Montenegro tied at the front of pack with 21 percent of support.
Montenegro's campaign was recently roiled by his admission that he received a nude photo from a state legislative staffer. The state senator denies any wrongdoing.
Pennsylvania special election: A contested special election for Pennsylvania's 18th congressional district will take place on March 13. Rep. Tim Murphy, R-Pa., resigned from Congress last year.
The race pits GOP state Rep. Rick Saccone, 60, against 33-year-old Democrat and former Marine Conor Lamb. The western Pennsylvania district has proven reliably Republican, but recent strong performances in special elections at the federal and state level have made Democrats optimistic.
A Gravis poll released this month found Saccone with a 6 point edge, while a Monmouth poll showed a 3 point advantage for the Republican.
The candidates will need to file financial disclosures by Thursday. The reports will show how much cash their campaigns have on hand to make their cases ahead of the election's final stretch.
Senate race in Tennessee: U.S. Rep. Marsha Blackburn became the leading GOP candidate for Tennessee's open U.S. Senate seat when Sen. Bob Corker, R-Tenn., decided to retire. However, Corker has reportedly reconsidered whether to run again as some Republicans in the state urge him to make a bid.
Blackburn says she will stay in the race no matter what, and her campaign initially suggested sexism drove concerns about her ability to win.
Corker tamped down those reports over the weekend, saying, "At this point, nothing has changed."