Democrats have the worst Senate map to contend with in at least a generation. There are 23 Democrats and independents who caucus with them running for re-election in 2024 while only 11 Republicans are on the ballot. Of the 10 most vulnerable senators, nine are Democrats.

Republicans are almost certain to pick up Joe Manchin's seat in West Virginia. That means if the GOP wins the White House or has a net pick-up of one seat, they will control the Senate.

There are targets aplenty, but the three most vulnerable Senate Democrats are running as hard as they can... away from the Harris-Walz ticket. Sens. Sherrod Brown (D-Ohio), Jon Tester (D-Mont.), and Jacky Rosen (D-Nev.) all have something better to do next week while the Democratic Convention is underway in Chicago.

The National Republican Senatorial Committee said in a memo this week that “Harris is arguably a bigger threat to Democrats’ Senate majority than Joe Biden." But the appearance of Harris and Biden at the same venue would no doubt reinforce the GOP's efforts to tie a Biden millstone around Harris's neck. This is something the three vulnerable Democrats can't afford.

CNN:

All of that raises the stakes for Senate Democrats to keep doing what they’re doing: touting their legislative accomplishments without invoking the Biden administration and using their fundraising edge to try to define their GOP challengers – often by mining their business backgrounds and out-of-state ties. Democrats have also been hitting back on attacks over the southern border by highlighting their support of bipartisan immigration legislation that Republicans killed in Congress this year.

But the risk for Democrats is that as their Republican challengers become better known, GOP campaign spending increases and more voters tune in, any separation from the top of the ticket will erode. Ticket-splitting isn’t as common as it once was, as CNN political analyst Ronald Brownstein wrote recently.

It's not unknown for senators in tough races to skip out on party conventions. But Harris has been making such a big deal about the Chicago convention being a Democratic Party love fest that the prospect of three major figures in the party absent from the big party should raise a few eyebrows in media circles (if they cared to report on it.).

In addition to the GOP's easy pickup in West Virginia (current Gov. Jim Justice is way ahead) the most attractive race for a Republican pickup is Montana, where Sen. Jon Tester is fighting for his political life against businessman Tim Sheehy.

Sheehy is up in most polls by about five points. Tester has yet to endorse Kamala Harris as the Democratic nominee, which should tell you a lot about the toxicity of Biden-Harris in Montana.

Republicans have run plenty of ads attempting to tie Tester to Biden and attacking him over the border. They are now likely to substitute the president for Harris, although Tester is among the few Democrats not to have endorsed her so far. Democrats, meanwhile, are trying to play up the contrast between the seven-fingered dirt farmer and his GOP opponent, Tim Sheehy, a wealthy businessman and retired Navy SEAL. Last Best Place PAC, a Democratic-aligned group, has run ads poking fun at what they call Sheehy’s “hobby ranch” and attacking him as a “millionaire out-of-stater driving up housing costs.” Democrats have also seized on Washington Post reporting about Sheehy’s changing account of a gunshot wound sustained roughly a decade ago to raise questions about his credibility.

The relevance of Sheehy’s relatively recent arrival in the state – he settled there in 2014 after leaving the military – has become a key question in this race. Democrats are trying to make it a weakness after using a similar argument to discredit Republican nominee Matt Rosendale in his 2018 challenge to Tester. But Republicans argue that post-pandemic Montana is filled with conservative transplants from bluer states and that Sheehy, who recently stepped down as CEO of Bridger Aerospace, has been a job creator.

Tester has a knack for pulling off unlikely wins in his Senate races. But this is the first time he will be on the same ballot with Donald Trump. And Trump won Montana by double digits in 2020.