Tuesday night’s primary voting in Wisconsin offered a perhaps revealing insight into Republican enthusiasm before Gov. Scott Walker’s recall election next month.

Milwaukee Mayor Tom Barrett won the Democratic primary to face Mr. Walker in the June 5 contest, beating Dane County Executive Kathleen Falk , the favorite of labor unions. Mr. Walker, who faced only nominal competition in the GOP primary, also won.

But Mr. Walker, in his primary, still managed more votes than Mr. Barrett and Ms. Falk combined, according to returns. The Republican received 626,538 votes, while the two top Democrats took 619,049 combined. Put together the total of all four Democratic candidates, and they manage to beat Mr. Walker’s total, taking 670,278 combined.

The state’s Republicans just went to the polls last month for the state’s presidential primary and will have to do so again next month for the actual recall. The fact they showed up en masse for a ceremonial GOP primary Tuesday suggests enthusiasm remains high. That fact was also on display this spring as GOP presidential hopefuls campaigned across the state: Most bumper stickers still carried Mr. Walker’s name rather than Mitt Romney’s or Rick Santorum’s.

Tuesday’s pro-Walker turnout is the latest sign the recall race remains a dead heat, said John McAdams, a political science professor at Marquette University in Milwaukee.

If Democrats say, “‘we have a big advantage in psychological engagement, we have a big advantage in mobilization,’ I’d say the Walker vote shot that all to hell,” Mr. McAdams said.