WASHINGTON — When Mitt Romney declared during his unsuccessful campaign for the Senate in 1994 that the federal minimum wage should rise with inflation, a break with Republican doctrine, both Democrats and Republicans accused him of pandering to Massachusetts voters.

Mr. Romney has now maintained that position for almost two decades, qualifying his stand as he sought the Republican presidential nomination but never relinquishing the view that inflation adjustments would be good for workers, good for employers and good for the broader economy.

As he prepares to accept his party’s nomination this week, his steady support for an idea vigorously opposed by conservatives and business groups underscores the complexity of predicting how he might manage the national economy.

During the current campaign, Mr. Romney has embraced the conservative view that government can best help the economy by getting smaller, and he has selected as his running mate Representative Paul D. Ryan, a Wisconsin Republican who is a standard-bearer for fiscal conservatism. But a review of the positions that Mr. Romney has taken on economic issues during his two decades in politics reveals a recurring tension between his political commitments and his private sector experience at Bain Capital, which he often cited earlier in his political career in advocating a larger government role in the economy.