The crowded field of Democratic presidential contenders has yet to produce even two or three short-odds favorites for the nomination. But the Republican race is rapidly narrowing down to two tough competitors: Vice President Bush and Sen. Robert J. Dole (Kan.).

Dole's solid early strength has come as an unpleasant surprise to the front-running Bush. Dole has been attracting both money and supporters at a faster pace than the Bush camp anticipated. With five months to go before the first caucus, the GOP nomination contest is shaping up into a close one -- a lot closer than Bush's people like.

"We have become competitive with the Bush campaign," Dole's campaign manager, Robert Ellsworth, told us. "They know they've got serious competition." A top Bush supporter insisted, however, that they had never underestimated Dole's strength.

Signs of strain are beginning to show between the two candidates, and it could break out into open feuding. President Reagan's famous 11th Commandment for party rivals -- "Thou shalt speak no evil of another Republican" -- may prove too constricting for a political infighter of Dole's scathing wit.

In fact, the opening skirmish may already have occurred, presaging a bare-knuckle brawl that could rescue at least the Republican half of the presidential race from eye-glazing boredom.

It began with Dole's appearance Aug. 24 in Texas, supposedly rock-solid Bush country. It was one stop in Dole's 30-state campaign swing during the congressional recess.

According to a Dallas newspaper, Dole's organizers "expected only 200 to 300 people" to show up at the reception. The candidate was greeted by "an enthusiastic crowd of 2,000" instead.

No doubt stung by this evidence of defection in his adopted state, Bush took an indirect slap at Dole in a speech the next day in San Antonio. He charged that Congress has "tied the president's hands" by trying to "micromanage" U.S. foreign policy. As Senate minority leader, Dole has publicly expressed misgivings about the president's foreign policy initiatives, so Bush's criticism clearly included Dole.

Never one to sit idly by in a political dogfight, Dole immediately and publicly denounced the vice president's remarks as "unfair." In a shrewd appeal to the GOP right wing, Dole said he and other congressional conservatives should not be lumped together with Reagan's liberal Democratic opponents on Capitol Hill.

The vice president's men have tried to use their candidate's front-runner status to scare off potential Dole contributors. They have said that Dole cannot hope to set up organizations in key states that will match the impressive state campaign machinery Bush has acquired over the years.

But a survey of Dole's organizational efforts in 37 states shows remarkable progress in his campaign's first six months. Even Bush supporters privately acknowledge that Dole has achieved much more than they ever dreamed he would.