Hillary Clinton’s increasingly confident campaign has begun crafting a detailed agenda for her possible presidency, with plans to focus on measures aimed at creating jobs, boosting infrastructure spending and enacting immigration reform if current polling holds and she is easily elected to the White House in November.

In recent weeks, as her leads over GOP nominee Donald Trump have expanded, Clinton has started ramping up for a presidency defined by marquee legislation she has promised to seek immediately. The pace and scale of the planning reflect growing expectations among Democrats that she will win and take office in January alongside a new Democratic majority in the Senate.

While careful not to sound as if she is measuring the draperies quite yet, Clinton now describes what she calls improved odds for passage of an overhaul of immigration laws — the first legislative priority she outlined in detail last year — and what could be a bipartisan effort to rebuild the nation’s roads, bridges, airports, rail system and ports.

She also could be immediately confronted with a choice about a Supreme Court vacancy that could set the tone for her relationship with Congress, and she plans to immediately champion new measures on campaign-finance reform and ending legal immunity for gun manufacturers.

Her campaign’s to-do list includes assembling a Cabinet that has women in roughly equal numbers to men and that otherwise reflects American diversity, and lobbying has intensified for those and scores of other jobs that Clinton would fill in her administration.

These 10 states are in play in the 2016 election. Here is where they're polling as of August and how much weight they'll have in November. (Sarah Parnass/The Washington Post)

Some Clinton boosters remain concerned that, with an election focused so heavily on Trump’s deficiencies, she could enter the White House without a clear mandate. But Clinton’s team is hopeful that a trouncing of her Republican opponent in November could soften the ground for a robust set of proposals that could be implemented both with and without congressional action.

“There’s nothing like winning to change minds,” Clinton said this month.

How she builds relationships on Capitol Hill, especially with Republicans, will be one key measure of success in the first year or so, Democrats said. A second crucial element will be how effectively she organizes a White House staff to keep the focus on her policy priorities and minimize the controversies that long have dogged Clinton and her husband.

The most significant unknown — and one that would determine to a great extent her ability to govern successfully — is how poisonous the political climate might be after a defeat of Trump, who has already begun complaining that the election system is “rigged” against him.

“Her greatest challenge will be the environment in which she comes to office,” said a former Obama administration official who spoke on the condition of anonymity to offer a candid view. “I don’t think any president has come to office underwater on their favorable image. This would be uncharted waters coming to office as an unpopular person. You don’t have a wellspring of goodwill to draw on, even in the first 100 days.”

Clinton named a five-member transition planning team last week — headed by former interior secretary Ken Salazar and including other familiar names in Democratic circles — that would eventually oversee the selection of Cabinet secretaries and thousands of lower-level officials. She also moved some top policy advisers over from her campaign to her transition team, a move that reinforced the notion that she is getting ready to govern.

The Fix's Chris Cillizza explains why Donald Trump demoted campaign chief Paul Manafort and added two new top advisers – Breitbart News chief Stephen Bannon and pollster Kellyanne Conway. (Peter Stevenson/The Washington Post)

Trump, who also has a transition team at work, trails by double digits in some national polls. No candidate in more than 60 years has come back to win after being so far behind at this point in the general-election campaign. Trump also is losing in surveys taken in battleground states where he is staking his campaign. Among those states is Virginia, where he has a 14-point deficit, according to a Washington Post-ABC News poll published in the past week.

Clinton has lately been telling Democratic audiences about her growing support among Republicans and touting what she says is a record of successfully working across the aisle to get things done. Her campaign regularly trumpets Republican endorsements and GOP disavowals of Trump.

It was a subject she treated gingerly during the toughest months of her primary contest against Sen. Bernie Sanders (Vt.), who challenged her from the left. Still, some liberal voters who backed Sanders in the primaries eye Clinton’s legislative priorities with a mixture of suspicion and high expectations.

If Clinton wins, she will be “under great pressure from the left to move on a whole host of issues. The pressure is going to be enormous, more so than on President Obama,” said Jim Manley, a Democratic consultant who was a senior aide to Sen. Harry M. Reid (Nev.) when Reid was Senate majority leader.

Manley said he is highly skeptical that Clinton will be able to get some of her more liberal proposals — such as raising taxes on millionaires — through Congress, even under the rosiest of election scenarios for Democrats. That tax is key to paying for the massive jobs-and-infrastructure package at the heart of Clinton’s promise to help rebuild the American middle class.

Manley is also less bullish about immigration reform — Clinton’s other signature issue — which has repeatedly failed in Congress. And he cautions that if Clinton seeks to implement her immigration agenda through executive action, as Obama has sought to do, she could immediately sour relations with Republicans in Congress.

Clinton has predicted that Democrats will retake the Senate and narrow the Republican majority in the House, a result that would potentially ease but not guarantee passage of some Democratic initiatives.

Democrats are unlikely to retake enough seats to amass a filibuster-proof 60 seats in the Senate, meaning Clinton would need Republican votes for nearly any important achievement.

Clinton has pledged to tackle an overhaul of what she calls a broken immigration system within her first 100 days in office and also has promised that the fix would include a means for illegal immigrants to gain U.S. citizenship.

“I’m hoping that the outcome of the election, which I am working hard to ensure [is] a victory, will send a clear message to our Republican friends that it’s time for them to quit standing in the way of immigration reform,” she said at a gathering this month of Hispanic and black journalists in Washington.

She also has promised to seek a multibillion-dollar package of infrastructure investments combined with various jobs incentives in the same time frame. Also on the 100-day list is introduction of a constitutional amendment that would seek to reinstate campaign finance rules swept away by the Supreme Court ruling in Citizens United v. Federal Election Commission. And Clinton has said she would seek legislation to end legal immunity for gun manufacturers right away — in what would be another immediate test of overcoming Republican resistance on the Hill.

“She has put out fairly detailed proposals, so in that sense, she has been very direct with the voters about what she could accomplish,” campaign press secretary Brian Fallon said. “If she wins, she will be able to point to the fact that she campaigned on a very specific set of policies in order to seek to hit the ground running and enacting as much of that platform as possible.”

But no one is drafting legislation now, Fallon said. “There’s a part of the process that can only come after she wins.”

Among other pledges, Clinton has said she would expand affordable housing, repair schools, rehabilitate failing water systems and connect every household to high-speed Internet by 2020.

She pledges to guarantee equal pay for women and improve affordable child care.

And a big, expensive one: make college tuition free for most families and debt-free for all while refinancing current student loan debt.

If Democrats do retake the Senate, longtime Clinton ally Sen. Charles E. Schumer (N.Y.) is expected to become majority leader. He shares Clinton’s impulse to seek common ground with Republicans, said a Democratic aide familiar with their past discussions.

Already, for example, there has been talk on Capitol Hill about whether Clinton should pair her infrastructure plan with an initiative more palatable to Republicans, such as corporate tax breaks.

Clinton chose Sen. Tim Kaine of Virginia as her running mate partly for his record of bipartisan cooperation and good relations across the Democratic spectrum. As vice president, Kaine would be tasked with pushing many parts of Clinton’s ambitious list.

Clinton has borrowed some of her economic policy agenda from the liberal Roosevelt Institute in New York, where president and chief executive Felicia Wong said the group has worked for six months to compile a list of “multiple hundreds” of people to recommend for administration positions.

“There’s no way to execute on that kind of ambitious policy agenda without excellent leadership,” Wong said, adding that she hopes that by pushing jobs and infrastructure first and getting bipartisan legislative victories, Clinton will be in a stronger position to push other parts of her agenda in Congress.

Similar lists of recommendations are coming in from other quarters, but Fallon declined to discuss any personnel plans.

Of roughly 4,000 political jobs to fill, more than 1,000 require Senate confirmation. Internal vetting, security clearances and ethics checks can take months.

Former Utah governor Mike Leavitt, who served in Republican President George W. Bush’s Cabinet and oversaw transition planning for Mitt Romney’s unsuccessful 2012 presidential campaign, said it is not too early to begin identifying candidates for roughly 300 jobs that are deemed “critical,” many of which require Senate confirmation.

“The first task is you have to put a team on the field,” Leavitt said, “and the task of getting a senior person into the job goes far beyond just choosing them.”