By Steve Holland and James Oliphant
WASHINGTON (Reuters) - Near the end of President Donald Trump's rocky first year in office, White House aides view imminent victory on a tax overhaul as a starting point to strengthen his weak approval ratings ahead of key congressional elections next November.
Some Republicans said any effort at a political turnaround must include reining in Trump's habit of lashing out at critics on Twitter.
White House aides said they recognized that Trump's poll numbers needed to start rising to limit the damage in 2018 elections in which his fellow Republicans' continued control of Congress will be at stake.
A Democratic takeover of the House of Representatives and Senate could jeopardize Trump's agenda.
"We have to grow, we have to move up, and I think having more successes like the tax vote will be important to us," said a senior White House official.
Administration officials said Trump would seek to use momentum generated from the biggest tax rewrite in 30 years to help propel other legislative priorities, including an infrastructure program and welfare reform.
Final passage of the Republican tax bill is expected on Wednesday in what would be Trump's first major legislative victory since taking office in January.
But the tax bill carries risks. Republicans insist it will boost the economy and job growth. Democrats condemn it as a giveaway to corporations and the rich. In a Reuters/Ipsos poll, some 52 percent of adults said they opposed the tax plan, while 27 percent supported it.
Unless Trump practices greater discipline, some Republican strategists see disaster looming in the congressional elections, in which a third of the 100-member Senate and all 435 seats in the House will be up for grabs.
"Stop tweeting and start the new year with a new level of message discipline. Just try it. It’ll work. And you’ll get those poll numbers back up," said Republican strategist Scott Reed.
"They’ve got to focus on that job approval number because it’s a historic death watch for midterm elections. The record is strong. His discipline is key for year two,” Reed said.
Trump has repeatedly caused controversy with early morning tweets, particularly those aimed at individuals. He raised hackles recently when he tweeted that Democratic Senator Kirsten Gillibrand "would do anything" for campaign donations.
"There are definitely moments that we’d all like to see stop," one senior aide said. "Some of the early morning stuff has not been helpful over the last few weeks."
There has been some talk in the White House and among Trump's outside advisers about hiring a senior political adviser akin to former President Barack Obama's political aide David Axelrod or former President George W. Bush's adviser Karl Rove.
The White House political director, Bill Stepien, is seen as a more data-driven adviser. Trump, who sees himself as his own strategist, does not have anyone steeped in politics like his former White House chief of staff, Reince Priebus, or former chief strategist Steve Bannon.
Aides said there was some discussion of getting Trump into events with smaller settings in order to show a more personal side of the president. His standard appearance is to go to an event, deliver a speech to a big crowd and leave.
Trump is up against a historical trend in which the party that holds the White House typically loses seats in the first congressional elections after a president's initial two years in office.
Democratic President Bill Clinton had a 46 percent approval rating in November 1994 and his party still lost 54 seats in the House and eight in the Senate. Trump was at 41 percent in a mid-December poll from NBC News and the Wall Street Journal.
Republican strategist Ford O'Connell said Trump had done much to keep his conservative base of support happy but had to expand his popularity. To do that, he needs to ease voters' concerns about his fitness for office.
"What he has to do to win over people like independents and never-Trumpers is make the American people feel comfortable with him as president," said O'Connell. "His achievements are quite striking, but he’s just not connecting (with the public).”
(Reporting by Steve Holland and James Oliphant; Editing by Caren Bohan and Peter Cooney)