Democrats in swing-state Senate races see boost amid Harris enthusiasm

Democratic Senate candidates in a handful of swing states saw their already-positive margins grow larger in recent weeks, according to a new Cook Political Report poll, as Vice President Harris’s shift to the top of the Democratic presidential ticket bolsters enthusiasm for the party.

Senate Democratic candidates in various swing states were already showing leads when President Biden was atop the national party ticket, and those margins have widened in almost every state contest since Harris replaced the president on the ticket last month, the Cook Political Report said Thursday.

The impact was observed most strongly in Nevada, where Democratic Sen. Jacky Rosen is now leading Republican challenger Sam Brown by 18 points — 54 percent to 36 percent. This is a jump from May, when she had a 7-point lead over Brown. These poll numbers, along with other recent surveys, resulted in the Cook Political Report shifting the race from “toss up” to “lean Democrat.”

In Arizona, Democratic Senate candidate and Rep. Ruben Gallego expanded his margin from 5 points over Republican candidate Kari Lake to 9 points (51 percent to 42 percent) in the same period, while Rep. Elissa Slotkin (Mich.) the Democratic nominee for the Michigan Senate seat, went from a 2-point lead to an 8-point one over former Rep. Mike Rogers (R-Mich.), 50 percent to 42 percent.

On the East Coast, Democratic Sen. Bob Casey’s (Pa.) lead over GOP nominee David McCormick increased from 8 points to 13 points, 53 percent to 40 percent.

Cook Political Report writer Jessica Taylor noted Wisconsin’s Senate race has remained “the most stable” since May, with Sen. Tammy Baldwin’s (D) lead over Republican Eric Hovde decreasing from 12 points in May to 7 points, 50 percent to 43 percent.

Harris’s entrance into the race quickly bolstered energy for the Democratic Party, which rapidly consolidated support around the vice president and her newly tapped running mate Minnesota Gov. Tim Walz. She became the party’s official presidential nominee earlier this month ahead of the Democratic National Convention next week.

Pointing to this uptick in enthusiasm, Taylor noted the margin by which Senate candidates need to outperform the party’s presidential nominee in red or swing states in order to beat their challengers has shrunk.

But while the shift in energy may have played a role in the candidates’ leads growing, Taylor wrote that the widening may suggest Democrats’ standing “may be more durable than Harris” since they were already enjoying strong leads before the ticket switch-up.

This standing is “bolstered by their significant cash advantage over Republicans and early, heavy ad spending in virtually every key contest,” Taylor wrote.

The poll also found undecided independents are starting to break towards Democrats, while Republicans and Democrats are maintaining their base voters at almost identical rates, Taylor said.

When the poll was taken in May across the five battleground Senate races polls, 42 percent of independents were voting for the Democratic candidate, while 31 percent were voting for the Republican candidate. Now, Democrats have a 21-point lead, with independents splitting 53 percent to 32 percent for Democrats.

The Cook Political Report summer battleground poll was taken in collaboration with the BSG and GS Strategy Group among 2,867 likely voters in Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania and Wisconsin. The poll was conducted July 26 to Aug. 2 and has a margin of sampling error of 1.83 points at the 95 percent confidence level.