Kander’s campaign said he received more than 20,500 contributions, about 94 percent of which were $100 or less. He has raised about $6.3 million since announcing his candidacy in February 2015. Blunt has raised more roughly $12.6 million over a longer period; he was raising money before Kander announced and had $2.2 million in the bank at the end of 2014.

Kander raised money at a pace of about $19,000 a day during the second quarter of this year. Blunt’s came in at a pace of more than $25,000 a day.

Blunt-Kander is one of about a dozen pivotal contests across the country whose outcome will determine control of the Senate in 2017.

Already, outside groups have begun spending on the race, mostly on Blunt’s behalf. Groups affiliated with Senate Majority Leader Mitch McConnell, R-Ky., and Republican operative Karl Rove have spent $2.2 million on ads praising Blunt’s Senate work on behalf of veterans. The groups announced recently they intend to spend another $2.5 million in September.

Kander’s fundraising has raised his national profile and moved the Missouri Senate race to one to watch. To this point, Senate races in presidential swing states of New Hampshire, Wisconsin, Pennsylvania, Ohio and Florida, all also involving Republican incumbents in tough re-election fights, have attracted more national attention.