Polls tighten to within margin of error in key races

With just days before Tuesday's vote, there's little daylight in the poll results between Democrat Hillary Clinton and GOP rival Donald Trump in their presidential bids.

And in the key races that will determine which party controls the Senate, a handful have tightened to within the margin of error. Democrats are hoping to turn four of those red Senate seats blue to win back control.

If Clinton wins the White House, Democratic control of the Senate would ease confirmation of her appointments, including a new Supreme Court justice. A Republican-controlled Congress could effectively thwart much of any Clinton presidential agenda.

If Donald Trump is the winner, a Democratic-controlled Senate could provide a check on his legislative agenda, which would prove harder to block if the GOP controls both chambers.

While a number of House races remain close, the Democrats have a much slimmer chance of capturing the 218 seats needed to wrest control from Republicans.

To take control of the Senate, Democrats need a net gain of four seats, for a total of 50, if Clinton wins. (With 50 seats, her running mate, Tim Kaine could cast a tie-breaking vote.) If GOP rival Trump becomes president, the Democrats need a net gain of five seats, giving them a 51-49 majority.

Of the eight Senate races considered toss-ups, seven are currently represented by Republicans: Illinois, Indiana, Missouri, New Hampshire, North Carolina, Pennsylvania and Wisconsin. In Nevada, Democrat Harry Reid is retiring, Republicans have a shot at picking up another seat.

Democrats appear to be on track to flip at least two of those seats. In Wisconsin, Democratic former Sen. Russ Feingold holds a polling lead against incumbent Republican Sen. Ron Johnson, according to the average poll results tracked by Real Clear Politics. In Illinois, incumbent Republican Sen. Mark Kirk has trailed Democratic challenger Tammy Duckworth in the polls, which have more recently widened in her favor.

If those trends hold, Democrats would need another two seats if Clinton wins, or three seats if Trump becomes president.

Here's how the remaining toss-up races break down, state by state:

Indiana

Though Indiana has typically been a reliably red state, the retirement of Republican Sen. Dan Coats has given an opening to Democrat Evan Bayh, a former governor and senator who retired in 2011. While the race is expected to be close, Bayh maintains a nearly 2.3 point lead in the polls, but that lead has been shrinking.

Missouri

GOP Sen. Roy Blunt held a comfortable lead through the summer, but his race against Democrat Jason Kander, Missouri's secretary of state, has tightened considerably, with just a 1.5 point edge — less than the margin of error. The final count is expected to be close.

Nevada

GOP Rep. Joe Heck is hoping to flip this Senate seat from blue to red, after the retirement of Senate Minority Leader Harry Reid. But Reid's handpicked replacement, Catherine Cortez Masto, has closed the gap, trailing by 1.4 percentage points. Heck has tried to distance himself from Trump, calling on him to quit the presidential race after the release of the "Access Hollywood" tape capturing his demeaning comments about women.

New Hampshire

Clinton's lead in the Granite State against Trump may also help Democratic Gov. Maggie Hassan in her bid to unseat incumbent Republican Sen. Kelly Ayotte, who has struggled to distance herself from Trump after earlier citing him as a role model for children. Ayotte is holding onto a slim lead in the polls.

North Carolina

While the state was once considered a safe Republican seat, incumbent Sen. Richard Burr is in a tough fight against Democrat Deborah Ross, a former state legislator, who briefly led Burr in the polls earlier this month. Burr's campaign has also benefited from Clinton's aggressive campaigning in the Tar Heel State, where Burr leads by 1.5 percentage points.

Pennsylvania

Democrats are also hoping to flip a Republican seat in Pennsylvania, where incumbent GOP Sen. Pat Toomey is trailing Democratic challenger Katie McGinty, who has opened up a 3.8 point lead. Pennsylvania has a split congressional delegation but has voted for Democrats at the top of the ticket in the last six presidential elections.