A horse-race update on the battle for control of the U.S. Senate

There are good reasons for Democrats to be upbeat about their chances of netting at least three Senate seats in the fall, which, combined with a Joe Biden presidential victory, would flip the chamber.

But while Democrats are on the offense in more states than a year ago, they haven't quite locked down the four overall takeovers they need. (Or three, plus a Democratic vice president to break ties.)

In a June 4, 2019, column, I wrote, "The Senate is broadly 'in play,' but Democrats need things to break just right to flip the chamber."

In a Sept. 4, 2019 column, I wrote that the "Senate landscape hasn't shifted dramatically, but the small change benefits Democrats. They currently have about a 4-in-10 chance to net at least three seats and win the presidency."

On April 20, I observed significant developments had occurred and Democrats no longer need an upset or two to win the Senate. The presidential race was looking better for them, newly developing Senate opportunities appeared interesting, and "the Democrats' initial top prospects have succeeded in proving their fundraising mettle and have taken advantage of Donald Trump's GOP."

That column argued that while the Senate was still a toss-up, "Democrats may just have the slightest of advantages."

Democrats have a growing list of opportunities. President Donald Trump's continued weakness, Democratic fundraising strength and issues such as the coronavirus and social justice continue to undermine Republican Senate hopes.

I've written repeatedly about Colorado Sen. Cory Gardner and Arizona Sen. Martha McSally's problems, so there is little reason to go over them again.

Gardner may have shaved a point or two off former Gov. John Hickenlooper's lead, and the senator is the better campaigner. But Colorado looks increasingly blue, and Hickenlooper will have to make multiple further mistakes to turn this contest into a real fight.

McSally trails by the low to mid-single digits against a challenger who has no lengthy voting record to attack. Arizona polling has been consistent, with McSally trailing Democrat Mark Kelly in public and private surveys.

Republicans have not given up on these races, but no incumbent wants to be behind at this point — especially where Biden is certain (Colorado) or likely (Arizona) to win.

The Republican Senate firewall always boiled down to North Carolina and Maine, though it's increasingly looking like a one-state firewall: Maine.

Maine appears to be the GOP's best chance to win one of the top four races and maintain control of the Senate.

Republicans acknowledge that Collins started with a big lead, but the race tightened. They now insist she has rallied and holds a lead in the mid- to high single digits. They dismiss public polling in the state conducted by PPP, a Democratic firm, and by Colby College (my alma mater), both of which show a narrow but clear lead for Democrat Sara Gideon.

Democrats point to the trend line in the ballot test and argue that Collins' initial lead has evaporated. They say she trails Gideon (on the ballot test but also on key questions), though the race remains too close to call.

Trump is running very poorly here, even though he lost the 2016 statewide vote by only 3 points. That cannot be good for Collins, a veteran with deep connections in the state who finds herself in trouble because she did not confront Trump as strongly as many former supporters expected.

This is one of those races where you simply have to decide which side you believe. Both sides have veteran, credible consulting teams, and it isn't clear why the two parties have such different data or perceptions of the contest.

Iowa probably belongs in the same category as Maine and North Carolina now.

Democrat Theresa Greenfield was an afterthought a year ago, but strong fundraising, grassroots enthusiasm and public and private polls suggest Iowa is now a toss-up. A June 7-10 Des Moines Register poll found Greenfield leading GOP Sen. Joni Ernst by 3 points, and Democrats have a similar assessment.

Greenfield's lack of a voting record is a problem for the GOP, and Ernst's falling job approval has given the Democrat an opening. Additional polling should clear up questions here, but Trump's weakness in the state (both in rural areas and in blue-collar, working-class parts of eastern Iowa) suggest a toss-up.

Montana's race is also close, with Gov. Steve Bullock competitive with Republican Sen. Steve Daines. But Montana is tougher territory for the Democrats, despite polls showing Biden and Trump close. Bullock must run far ahead of Biden to win, which makes Montana more difficult than Iowa for Democrats.

Democrats are not ready to throw the towel in on Alabama Sen. Doug Jones, who won a 2017 special election against widely mocked Republican Roy Moore. But Alabama's strong GOP bent — and Trump's expected comfortable victory — makes Jones an underdog.

Kansas state Sen. Barbara Bollier is a strong candidate for the Democrats there, even with state Rep. Roger Marshall defeating Kris Kobach in Tuesday's Republican primary.

In Georgia, Republican incumbent David Perdue leads Democrat Jon Ossoff by the mid-single digits in public polls, but Trump and GOP Gov. Brian Kemp's mishandling of COVID-19 could hurt Republicans, and turnout is always a huge factor. Democrats probably need a national wave to flip this seat.

Finally, Democrats are watching Alaska, because of (1) its quirkiness and (2) the appeal of independent Al Gross, who has Democratic support against GOP Sen. Dan Sullivan.

Republican targets have all but dried up with Trump's problems. That means Democratic seats in Michigan, New Hampshire and Minnesota don't appear to be at risk.

Democrats have multiple paths to a Senate majority. Just as importantly, Trump defines the election, a headache for Republicans and a boost for Democrats.