WASHINGTON (AP) — President Barack Obama has the upper hand in the fierce struggle over immigration now taking shape, with a veto pen ready to kill any Republican move to reverse his executive order, Democrats united behind him and GOP congressional leaders desperate to squelch talk of a government shutdown or even impeachment. With the public favoring changes in the current immigration system, the Republicans' best short-term response appears to be purely rhetorical: that the president is granting amnesty to millions, and exceeding his constitutional authority in the process. Neither of those is likely to satisfy the tea party adherents in Congress — or the Republican presidential contenders vying for support among party activists who will play an outsized role in early primaries and caucuses just over a year away. When the newly elected representatives of the people take their seats, they will act, said McConnell, who will become majority leader when his party assumes control of the Senate in January. Democrats counter that it's been about 17 months since the Senate passed the bipartisan bill. [...] opponents in the House have pressured Boehner successfully not to allow it to come to a vote. Senate Majority Leader Harry Reid, D-Nev., envisioned a different outcome when asked if a future Republican president might reverse Obama's actions, potentially subjecting millions who step forward now to get work permits to being deported in the future.