While America did have a two-party system before 1854, the year the Republican Party was founded, it was the Whig Party along with the Democrats who were the political superpowers of the day. According to Wikipedia, however, the Whig Party "was ultimately destroyed by the question of whether to allow the expansion of slavery to the territories."
In other words, the political party imploded because it attempted to do the impossible...find a middle ground with a morally repugnant issue like slavery, which runs contrary to the very principles this great country was founded.
The Republican Party of today faces a similar situation as the Whigs did in the 1850s. With the Democrats choosing to side with abortionists in the wake of Roe v. Wade for political and financial reasons, the Republicans stepped in to fill the void. The Democrats at the national level abandoned the "Reagan Democrats" -- mostly conservative Catholics from the larger established cities -- and the Republicans won them over with their clear pro-life platform.
Like everything else in politics, things change. Today, a leading candidate for the Republican presidential nomination, former New York Mayor Rudy Giuliani, is a clear pro-abortion advocate. He has a horrendous record of life. The National Catholic Register wrote a compelling editorial in its most recent edition that clearly explains why Mayor Giuliani is unacceptable for pro-lifers.
The article ends with this ominous warning for the Republican Party: The bottom line: Republicans have made inroads into the Catholic vote for years because of the pro-life issue. If they put a pro-abortion politician up for president, the gains they’ve built for decades will vanish overnight.
Ironically, the Republican Party rose to prominence by speaking out unapologetically against the most significant moral evil the country faced. It was not an easy road, and 625,000 Americans lost their lives in the civil war that ensued over granting the most basic of human rights.
Today, the Republican Party isn't just undermining to fix the advances that it made since the 1970s when it started drawing in Catholics and other professional lifers, however it is additionally toying with its remarkably presence. Like in the 1850s, this solid square of individuals won't rush back to the Democrat party since they have officially sold their spirits to the fallen angel over premature birth. More probable, another political gathering will rise that could see the Republicans go the method for the Whigs.