WE'VE NEVER been sure precisely what card to ask for from a "card-carrying" Democrat, but again yesterday, party loyalists gasped in the House as they witnessed a dramatic demonstration of what they consider errant behavior on the part of too many colleagues (translation: they're tipping away from Tip in droves on the big votes).

When 48 Democrats fall in behind President Reagan as they did on the tax bill vote, you'd better believe that the in-House partisan anxieties extend well beyond any ultimate economic consequences of this latest decision. Besides the question of future Democratic leadership, there has beren considerable discussion about how to deal with those who keep breaking ranks. Answer? Carefully, until somebody at Democratic Central proves that "party discipline" isn't a contradiction in terms.

Obviously, Mr. Reagan hit home with his prime-time TV pitch for his tax bill -- sending more than a few congressional Democrats to their next-day floods of mail and messages for clues on how to behave for yesterday's roll call. But even before this vote, there were petitions making the rounds calling for punishment of Democrats who act too much like Republicans.

Drastic action, if any such thing were to be attempted, could include tossing members out of the party caucus or taking away any impressive committee assignments they may enjoy. Fat chance: Having toleratged Sen. Harry F. Byrd Jr. of Virginia, who ages ago declared himself an independent and who wouldn't even life a finger for the Democratic presidential nominees, congressional Democrats would be hard-pressed to make an in-House case against anyone -- at least until next year.

Besides, how do you define partisan treason? Get too tough and a suspected traitor may just go ahead and become one officially; that, presumably, is why nobody is scheduling any honest-to-goodness official action on the petitions. Still, you do sort of sympathize with those Democrats who have watched their majorities evaporate, and who have seen two of their Texas brethren -- Reps. Phil Gramm and Kent Hance -- slipping off to join GOP strategy meetings on budget and tax legislation.

Another Texas, Majority Leader Jim Wright, has said that "if you wear the jersey and are privy to the huddle, you shouldn't be allowed to tell the plays to the other team." That's fine for football as sports fans know it, but political football is something else -- and all the players in Congrees know that it's the home-team fans who hold those options to renew their contracts. The best recourse, to take this analogy one final yard, would be to get a better game plan for the whole team.