Democrats have a slight lead in the latest generic congressional ballot from Harvard/Harris poll, but Republicans have an edge with likely voters.

By The Numbers:
Fifty-one percent of voters say they’ll support the Democrat candidate for Congress in November, and 49% say they’ll support the Republican. Among likely voters, however, only 49% say they’ll support the Democrat and 51% say they’ll support the Republican.
Sixty-nine percent of voters are motivated to vote for their party, as opposed to 31% who are motivated to vote against the other party. By party, 79% of Republicans and 71% of Democrats are motivated to vote for their party. Independents are split: 55% say they’re motivated to vote for a party; 45% are motivated to vote against.
The Bottom Line: This is the first good news for Republicans after several weeks of negative polling and race ranking updates. These numbers suggest Republicans are motivated to turn out for their incumbents, and potentially flip Democrat-held seats. One poll does not make a trend, however, so GOP candidates need to harness this enthusiasm and continue to convert voters who are on the fence about giving the party in power more time to fix the problems.