Republicans seem to have all the momentum lately when it comes to the battle for control of the U.S. Senate.
GOP chances were already looking brighter because of the drag on Democrats from the Affordable Care Act and President Obama's low approval ratings. Then came two developments that suddenly expanded the playing field: Former GOP Sen. Scott Brown recently announced his intent to run against New Hampshire Democratic Sen. Jeanne Shaheen, and GOP Rep. Cory Gardner jumped in against Colorado Democratic Sen. Mark Udall.
That makes 12 states with competitive races, according to the Cook Political Report's latest update.
Democratic incumbents currently hold 10 of those seats; three of them are retiring. Republicans need to win a net of just six seats to become the Senate majority.
While their chances of doing that are clearly rising, political consultant Steve McMahon of Purple Strategies cautions against underestimating the advantages of the Democratic incumbents who will be on the ballot in November.
"The states that they are running in are states they have run in before, that they understand well and have been elected to, some repeatedly," said McMahon. "They're the kind of Democrats that match the state well."
As incumbents, they can point to all they've done for their states and they usually can raise the money they need, McMahon said. And he gives Republicans credit for producing a solid field of candidates.
"They've done a great job of recruiting this year. They've run many of the nut jobs out," McMahon said. "But they still do have primaries and primaries weaken candidates."
The president's weakness in the polls, the Affordable Care Act and widespread anxieties about the economy aren't the only factors working in favor of the GOP. Republicans also have a big advantage on voter intensity.
"We always look at the question, how interested are you in the upcoming elections on a 1 to 10 scale, with a 9 to 10 being the most interested," said Neil Newhouse of Public Opinion Strategies, a Republican research firm, who pointed to a recent Wall Street Journal/NBC News poll his firm did with Hart Research Associates.
"In a presidential election, it doesn't mean as much because everybody votes. In a midterm election, where you're looking at 40 percent turnout, it does make a difference. ... Among voters who rate their interest a 9 or 10, Republicans have a 15-point advantage, 53 [percent] to 38 [percent]. So you have Republicans now gaining the same kind of intensity they had in 2010. It's like our guys are campaigning downhill as opposed to the Democrats."
2010, of course, was the year of the historic midterm landslide in which Republicans captured 63 seats — and House control. They gained six Senate seats that November. And that was after Brown won a January special election for the Massachusetts seat long occupied by Democrat Edward Kennedy.
If this year's Republican intensity results in a 2010-style wave, there could be some surprising races, Newhouse said. Virginia and Oregon, for example, might seem like real long shots for Republicans at the moment but they might be within reach in that kind of year, he said.
With an expanded playing field and the real prospect of a flip in Senate control, both parties and their outside-group allies are likely to spend a record amount during this year's midterms.
Independent expenditures for the 2014 election cycle through March 20 have already reached $39.2 million, according to the Center for Responsive Politics.