Sen. Lloyd Bentsen D-Tex.), one of the principal architects of the Democratic sweep in last fall's elections in Texas, is sending signals that he believes former vice president Walter F. Mondale is the strongest Democratic presidential candidate for 1984.

Officially, Bentsen intends to stay neutral because he is chairman of the Democratic Senatorial Campaign Committee, according to his aides.

But at least one important Bentsen supporter in Texas signed on with Mondale's campaign after receiving a call from Bentsen and later from Mondale, and another prominent Texan close to the senator said this week that he expects to support Mondale. This would influence Bentsen's extensive network of supporters in the state.

As evidence of his evenhandedness, Bentsen aides say he has steered friends to the campaign of Ohio Sen. John Glenn. But Bentsen recently told friends he believes that Mondale has a sizable head start for the Democratic nomination, including Texas, which many politicians have considered too conservative for the liberal Mondale. Bentsen also has said privately he is not impressed with the effort Glenn has made in Texas.

The conservative senator, who easily won reelection, organized and partly financed the massive get-out-the-vote effort credited with helping Democratic Gov. Mark White defeat incumbent Republican Gov. Bill Clements and bringing a statewide slate of young, progressive Democrats to office.