As we go into the Republican National Convention, Hillary Clinton is a solid 4 points ahead of Donald Trump nationally and is beating him in swing states from North Carolina to Ohio to Florida.

It’s easy to forget that this wasn’t inevitable. Republicans’ disadvantage this year is largely a result of unforced errors — principally among them the nomination of Donald Trump. Here’s a very plausible alternate history of the past year in which Trump never ran, Marco Rubio became the nominee, and Republicans were, as a result, poised for a tremendous victory in both 2016 and beyond.

Republican presidential nominee Marco Rubio is sitting in a commanding position as we head into the 2016 Republican National Convention. The latest poll averages show Rubio beating presumptive Democratic nominee Hillary Clinton by 4 points nationally, with an edge in his home state of Florida.

Rubio is also expected to get a polling bump in Ohio after picking as his running mate Gov. John Kasich, who remains hugely popular in this crucial swing state. And he's making appeals to Latino voters, helping the Republican Party make up ground on some of its longstanding demographic disadvantages.

It’s hardly surprising that Rubio is the clear favorite to win in 2016. Parties rarely take three presidential elections in a row (as Democrats are trying to do this year), the economy is good but not great, and according to most political science models, that translates into high odds of Republican victory. Emory political scientist Alan Abramowitz's "Time for Change" model, for example, finds that if the tepid first quarter GDP growth rate of 0.8 percent keeps up, Rubio should beat Clinton, 51.4 percent to 48.6 percent.

A Rubio victory — along with expected down-ballot GOP gains — would give the Republican Party overwhelming dominance in American politics come 2017, allowing the GOP to steer the country in a far more conservative direction, dismantling Obama’s agenda and reshaping the Supreme Court. Here’s a recap of how we got to this point.

Rubio beat back a surprisingly strong challenge from Ted Cruz in the primaries

Throughout the GOP primary, it was clear that Marco Rubio, the establishment’s choice, had a strong edge in the race over most of the other candidates.

Retired neurosurgeon Ben Carson experienced a boomlet, briefly leading in Iowa in September, but proved to be this cycle’s Michele Bachmann or Herman Cain: a short-lived phenomenon who appeals to base conservatives but fizzles out quickly. Rand Paul tried to recapture his father’s libertarian base, but his wishy-washy stance on ISIS alienated the isolationist voters who should’ve kept him afloat.

Chris Christie and Kasich both had the potential to be serious candidates, but Christie was still hurt by the residual taint of his Bridgegate scandal, and Kasich’s tacking toward the center alienated GOP base voters. Most surprisingly, the well-funded Jeb Bush proved to be an extraordinarily inept campaigner, and much of the establishment support that should’ve gone to him flowed instead to Rubio.

For a brief moment it appeared the entire race might be upended by the entry of eccentric billionaire Donald Trump, until Trump — as he has always done in the past — opted at the last minute not to run.

Rubio’s only serious challenge came from Ted Cruz, who, because of his constant fights with the GOP establishment and strong anti-immigration bona fides, became the consensus conservative favorite. Social conservative leaders like Bob Vander Plaats, Richard Viguerie, and Tony Perkins rallied to Cruz’s side, and state-level Tea Parties broke heavily in his favor.

Cruz won the Iowa caucuses, but Rubio then beat Cruz soundly in New Hampshire, a state not much given to social conservatism. Then, buoyed by the support of Gov. Nikki Haley, Rubio won South Carolina. Bush, Christie, Paul, and Kasich all quickly dropped out after dismal showings. Cruz and Rubio kept sparring for the next few months, but Rubio’s decisive victories in Florida, Ohio, and Illinois meant he had the primary wrapped up by March.

The result is that Rubio has had months to get his general election operation up and running. He’s extensively staffed up in key early states, with his campaign and friendly Super PACs collectively placing 600 staffers in Virginia alone by some reports.

Their fundraising has broken records, with Rubio, the party, and Super PACs collectively garnering $500 million so far — well above the $410 million raised by Hillary Clinton and her allies — in part because of a recent coordinated, successful push among hedge funders worried by rumors that Clinton will pick Elizabeth Warren as her running mate.

Hillary Clinton has struggled to wrap up the nomination

Meanwhile, in the Democratic primary, Clinton has had to deal with a spirited challenge from Bernie Sanders, the previously obscure 74-year-old democratic socialist senator from Vermont. Clinton’s huge level of support among black voters led to a clean sweep of the South and gave her an imposing delegate lead early on, but Sanders picked up steam thereafter, winning contests in Michigan, Wisconsin, Indiana, Oregon, and Washington.

One of Clinton’s biggest challenges throughout the primary has been the polls showing that she matches up poorly with Rubio — especially compared with Sanders. While the Clinton camp insists that this is just because Sanders isn’t well-known, and that he’d be far more vulnerable in a general election, this became a potent talking point for the Sanders camp as he stayed in the race.

Sanders is now insisting he will take the fight to the convention and plead with superdelegates to back him as the only candidate capable of stopping Rubio. There are some signs that the ploy could work; reports indicate that some liberal superdelegates who endorsed Clinton, like Sens. Sherrod Brown (D-OH) and Tammy Baldwin (D-WI), are preparing to vote for Sanders at the convention. It doesn’t help that FBI Director James Comey recently castigated Clinton at length as "extremely careless" over her handling of State Department emails — a quote the Sanders and Rubio camps are repeating ad nauseam.

Privately, Clinton campaign chair John Podesta and Sanders chief strategist Tad Devine are meeting and attempting to come to an accommodation that would see Clinton at the top of the ticket but include numerous concessions to Sanders. The Clinton camp has already committed to calling for a federal $15-an-hour minimum wage, the rejection of the Trans-Pacific Partnership, and free college for all in the party platform.

But the real sticking point of the talks is the VP slot. Devine and Sanders campaign manager Jeff Weaver had floated the idea of Sanders on the ticket, but Clinton considers his age and personal antipathy toward her a nonstarter. Podesta’s counteroffer was widely reported as being Elizabeth Warren on the ticket in Sanders’s stead: a major concession, considering how powerful the specter of Vice President Warren has already become as a Wall Street fundraising tool for Rubio.

Republicans are poised to dominate American politics after this election

Rubio isn’t just a strong candidate in this election — his success also bodes well for the GOP’s future. Polling from groups like Latino Decisions and Washington Post/Univision are showing Rubio far outperforming Mitt Romney among Latinos — a fact that could swing states like Florida, Nevada, and New Mexico his way.

Nor is this merely a short-term phenomenon. Rubio’s election, especially if coupled with a GOP push for business-friendly immigration reform once in office, could signal a long-term realignment of the parties, with growing Republican support among Latinos bolstering the party’s presidential prospects for years to come. Rubio provides a path for the party to follow in coping with America’s ongoing demographic transition.

Rubio also has the potential to firmly secure Wall Street and Silicon Valley as close allies of the GOP. The former has been moving right ever since Dodd-Frank, but Rubio has done a tremendous job of courting the financial sector this year. His enthusiasm for high-skilled immigration, and rhetoric on innovation and deregulation, has won over venture capitalists and tech executives who fear the Warren wing of the Democrats almost as much as the finance industry does.

The specter of an unpopular Clinton at the top of the ticket may also hurt Democrats’ down-ballot efforts. The party has had a tough time recruiting strong candidates: Former Sen. Evan Bayh (D-IN) has declined to run again for his old seat, for instance. Current odds suggest Republicans will keep control of both the Senate and House after November.

That sets up 2017 to be the first year in more than a decade when Republicans have unified control of the federal government, enough to pass the huge tax cuts, the low-income program cuts, and, quite possibly, the entitlement reforms that both Rubio and House Speaker Paul Ryan have backed. Rubio is also expected to put a priority on higher defense spending and a more extensive anti-ISIS mission early on.

And that’s just the beginning: Republicans are already dominant at the state level and benefit from a more favorable electorate in midterms. That sets them up well for the 2018 midterms — and they are now well-positioned to gain seats over Rubio’s first term, much as they did in 2002.

And then there’s the Supreme Court. If elected, Rubio would be able to replace the late Justice Antonin Scalia with a stalwart conservative. And he may get a chance to leave an even bigger mark on the Court: Ruth Bader Ginsburg is aging and has chronic health issues, Anthony Kennedy is about to turn 80, and Stephen Breyer is 77.

If all three retired, the Court could swing from having four liberals, three conservatives, and a swing vote (Kennedy) to having two liberals and seven conservatives. Rubio may have the chance to secure a lasting right-wing majority on the Court for decades to come.

These are the stakes of the election. If Rubio wins, he could realign the electorate in a way that permanently improves Republicans' odds by making inroads with Latinos; he could greatly expand the party’s support in the business community, denying Democrats crucial sources of fundraising; he could enact a top income tax rate of 25 percent and pass his proposal to abolish taxes on capital gains and dividends entirely. He could put in place the most conservative Supreme Court in nearly a century.

Clinton still has a chance to turn this around, but unless she does, it looks like the dawn of a new conservative epoch is upon us.