The midterm math for Democrats in the Senate is dismal.  They have 26 seats to defend (plus two independents), while Republicans have just nine seats at risk this November.

To make matters worse for Democrats, ten of those incumbent senators are running in states won by Donald Trump in 2016. 

Republicans are in much better shape, with only two or three incumbents who will be seriously challenged.  With a margin in the Senate of only two, it would make life a lot easier for the GOP if Republicans could pick off a couple of those vulnerable Democrats.

At the moment, all ten of the incumbent Democrats running in states won by Trump are massively outraising any GOP challengers.

The Hill:

Talking Points Memo reported that most of those 10 Democrats have at least doubled the fundraising of their Republican opponents.

In addition, half of those Democrats have at least four times as much cash on hand as their top funded Republican challenger.

The Democrats facing the difficult 2018 midterms include Sens. Tammy Baldwin (Wis.), Joe Manchin (W.Va.), Sherrod Brown (Ohio), Bob Casey (Penn.), Jon Tester (Mont.), Bill Nelson (Fla.), Joe Donnelly (Ind.), Debbie Stabenow (Mich.), Heidi Heitkamp (N.D.) and Claire McCaskill (Mo.).

McCaskill enjoys the widest gap in funding, with $11.2 million in her campaign account compared to Republican hopeful Missouri Attorney General Josh Hawley's $2.1 million.

Tester and Casey also have multi-million-dollar advantages in total funding over their GOP opponents, according to the data.

McCaskill, Donnelly, Nelson and Heitkamp are considered among the most vulnerable Democrats in the Senate heading into the November midterm elections. Democrats are hoping to take back control of the House, but face a more difficult path to earn majority control of the Senate. 

It's not surprising that incumbent senators have massively outraised any GOP opponent.  They've been raising money for several years, and most GOP challengers are trying to win their primaries.

The key will be what happens when the smoke clears and one Republican challenger is left standing.  At that point, the money will start rolling in for the Republican, and it will be up to him to make the most of it.

The two most vulnerable Democrats – Senators Heitkamp and McCaskill from North Dakota and Missouri – have done a good job over the years in tending to the home folks and not taking outrageously liberal positions on the issues.  But Republicans have a decided registration advantage in both of those states, and with a superior effort to get out the vote, they will have a better than even chance of taking at least one of those seats.