One year ago it would have been hard to picture both the Arizona and Connecticut open-seat Senate races as Tossups with less than a month to go before Election Day. But funny things can happen to the Senate battleground map based on candidates and the campaigns they run — just ask Republicans this cycle about Missouri.

The open-seat Senate races in the Nutmeg State and the Grand Canyon State are thousands of miles apart, yet share some distinct similarities. Both feature House Members who began the race as the heavy frontrunner and challengers who have surged based on the strength of their campaigns. Those challengers will still have to overcome a heavy partisan disadvantage at the presidential level, but that prospect seems to be increasingly possible. Therefore, we are moving both races into the tossup column, even though in both races, the party that currently holds the seat still has a very small advantage.

On the House side, four of our ratings changes are in the direction of Democrats while three are benefiting Republicans. Both parties continue to move TV ad reservations from less competitive races to more competitive ones, giving us a clearer focus each week about the House battleground map. You can view all of our Senate ratings

from less competitive races to more competitive ones, giving us a clearer focus each week about the House battleground map. You can view all of our Senate ratings here and our House ratings

and our House ratings here.

Here are the race ratings changes we are making today:

• Arizona Senate: Leans Republican to Tossup
  Rep. Jeff Flake (R) is in an unexpected dogfight with former U.S. Surgeon General Richard Carmona (D). Flake was dark on television for much of September, but now he is fighting back. Both national parties are all in here, outside groups are spending big money, and on Wednesday night President Bill Clinton campaigned for Carmona. Flake might be able to break away with a new negative ad and a strong debate performance Wednesday night. But for now, this one could go either way.

• Connecticut Senate: Leans Democratic to Tossup
  Democrats insist this race is not on par with other Tossups, but their actions in support of Rep. Christopher Murphy (D) speak loudly. Outside groups have rushed money into the state to counter GOP nominee Linda McMahon’s self-funded, months-long spending blitz. Both sides are engaged now, and there is really one question: Can McMahon withstand the negative ads coming her way?

• Florida’s 2nd district: Likely Republican to Leans Republican
  Even though freshman Rep. Steve Southerland’s (R) Florida Panhandle district got a bit less Republican in redistricting, he really should be fine. That doesn’t mean the race hasn’t closed in recent weeks as national Democrats came into the district to knock the incumbent on air. The National Republican Congressional Committee, in its first serious foray in the Sunshine State this cycle, came to his defense, which should help him hold on. But this is more of a race than it was a month ago.

• Florida’s 10th district: Likely Republican to Leans Republican
  GOP Rep. Daniel Webster’s campaign, in his comfortably Republican district, has been, well, very underwhelming, especially for a man who is a longtime politician. The Democratic Congressional Campaign Committee announced today that it had begun walloping him with a half-million dollars worth of ads. Val Demings, the Democratic nominee, is a strong candidate, but she’s still more likely than not to lose this Orlando-area seat.

• Illinois’ 13th district: Leans Republican to Tossup
  Democrats have gone in big in this downstate district with five different spots targeting GOP nominee Rodney Davis, a former top aide to Rep. John Shimkus (R-Ill.). Republicans are still confident they can keep this seat because they see emergency room doctor David Gill (D) as a flawed candidate. Regardless, heavy spending here has made it a Tossup race.

• Kentucky’s 6th district: Likely Democratic to Leans Democratic
  Rep. Ben Chandler (D) faces a rematch with his 2010 opponent, attorney Andy Barr, after the Republican came up just short of winning two years ago. All signs point to this race not being near as close as it was the last time, and Chandler was no doubt helped by redistricting. But outside money is flowing to this race, and the demographics of the state and district still heavily favor Republicans. Chandler is still the favorite to win re-election, but it’s no cakewalk — and likely never will be.

• Michigan’s 1st district: Tossup to Leans Democratic
  Republicans are increasingly concerned about Rep. Dan Benishek’s (R) prospects in this Upper Peninsula district. It’s part of the reason he earned a spot on Roll Call’s most recent Top 10 Vulnerable Members list. Other reasons include recent surveys that show his opponent, former state Rep. Gary McDowell (D), taking the lead.

• New Jersey’s 3rd district: Leans Republican to Likely Republican
  A year ago, attorney Shelley Adler was a top Democratic recruit to unseat Rep. Jon Runyan (R). Then on Wednesday, the committee pulled television ad reservations in the Philadelphia market. It is not just a triage move — it is a sign of a lack of confidence. The hopes for Democrats to win this seat, especially after Republicans benefited here from redistricting, seem to be tied to whether there is a national wave. And there is none this year.

• Pennsylvania’s 8th district: Leans Republican to Likely Republican
  Both the DCCC and the National Republican Congressional Committee have started pulling buys from the Philadelphia market, which covers this district and the nearby New Jersey race. It’s not a strong sign for attorney Kathy Boockvar’s (D) chances of defeating Rep. Mike Fitzpatrick (R).

— Abby Livingston, Shira Toeplitz and Joshua Miller contributed to this report.