There are no plans on the table now for Mitt Romney to dip into his personal fortune, as he did four years ago, to bankroll his candidacy, several campaign advisers said this week, even as the battle for the Republican presidential nomination increasingly looks like it will be a long and expensive fight. Romney by far leads the GOP field in fundraising, taking in about $75 million through the end of last month. But his campaign continues to spend heavily in key states in its effort to quell the rise of Rick Santorum, whose once woeful fundraising nearly matched Romney’s last month.