Republican incumbent Sen. Marco Rubio remains favored to win a second term against Democrat Patrick Murphy, but for the first time in a couple of months, it feels like Rubio is no longer an overwhelming favorite.

At the very least, it is increasingly likely that the Democratic Senatorial Campaign Committee and the Democrats' Senate Majority PAC, which pulled money out of the race, may wake up Nov. 9, see a narrow Rubio victory, and regret pulling out too soon.

Clearly, the more Donald Trump loses ground and turns off vast swaths of the electorate, the more Rubio needs to worry. He probably can survive Hillary Clinton carrying Florida by 2 percentage points, but not necessarily 5.

"I think Marco's probably in good shape, but he can't take anything for granted because it's an election year like none we've ever seen before," said Republican consultant Mike Hanna of Tallahassee. "(Trump) is the wild card, not only for Marco but a lot of Republicans down the ticket. … It's not going to be a good year for Republicans."

It has been a good week for Murphy:

• He held his own against experienced debater Rubio in their first televised debate Monday night. In fact, it's political malpractice that Murphy's campaign turned down several debate invitations, given how little known he remains to most Floridians.

• A second poll this month shows Murphy trailing the Miami Republican by just 2 percentage points. Those polls by Quinnipiac University and Wall Street Journal/NBC show a margin-of-error race, though the RealClearPolitics.com polling average has Rubio leading by 4.2 percentage points, slightly better than Clinton's Florida lead of 3.6 points.

• Even Rubio's hometown newspaper, the Miami Herald, endorsed Murphy.

"Beyond the political differences, there are issues of sincerity and character for voters to consider. First, he reneged on his unequivocal pledge not to run for re-election for a position he once openly disdained — but only after he lost his bid for the Republican presidential nomination to his nemesis, Donald Trump," the Herald's editorial board wrote. "Then he endorsed Mr. Trump, whom he called a con man during the campaign. And still at this late date, he continues to stand by that endorsement, even as the Republican candidate stumbles from gaffe to insult to outrage."

Rubio has started to show signs of nervousness. In Monday's debate — two days after he declined to utter Trump's name in a speech to Republican activists in Tampa — he sought to put more distance between himself and Trump, whom he supports. Rubio said that he doesn't trust either nominee and that it's a "horrifying" and "disturbing" choice between Trump and Clinton.

He also appears to be stepping up his attacks on Murphy, even bringing up an old Facebook photo of Murphy and an ex-girlfriend during the debate to depict Murphy as a groper.

The Democrats' shot at winning a Senate majority is looking better amid Trump's struggles, and national Democrats clearly see easier, less expensive opportunities in states like New Hampshire, Indiana and North Carolina. But another little-noticed Trump effect could help Murphy. Because Trump and his allies are spending relatively little on Florida's TV airwaves, the state's ad rates are not rising nearly as much as expected for the final weeks of the campaign.

Rubio remains the clear front-runner, but this is still a race.

Contact Adam C. Smith at asmith@tampabay.com. Follow @adamsmithtimes.