WASHINGTON — Congressional candidates and their outside benefactors are on track to spend at least a record $2.3 billion to influence the outcome of Tuesday’s vote, underscoring the expansive role of super PACs on Capitol Hill even during an election dominated by the presidential race.

Expenditures by the candidates themselves might not eclipse the records set in 2010, election watchdog groups say, but deep-pocketed special interest groups are spending with abandon.