The Republican Party has lost its roots in recent years, and when one looks at the principles of its leaders over the past 156 years, it has very little similarity to the viewpoints of its most famous political figures!
It is no longer the party of Abraham Lincoln and other Republicans who founded the party in 1854, fought against the Confederacy in the Civil War, and promoted the end of slavery and advocated racial equality! Now the Republican party sounds more like the Confederate mentality, and has very little appeal among African Americans! The South is the strongest section of Republican support, when in the past, to be a Republican was anathema in the Old Confederacy!
It is no longer the party of Theodore Roosevelt, George Norris, Robert LaFollette, Sr., and other Progressive Republicans who wanted social and economic justice and regulation of big business in the early 20th century! Now, the word “progressive” is trashed, not only by Republican leaders, but by conservative talk radio and Fox News Channel hosts who make being a “progressive” a great evil! And certainly, the Republican party does NOT care for social and economic justice or regulation of corporations, as evidenced by the disastrous policies that have led to the Great Recession! 
It is not the party of Dwight D. Eisenhower, a moderate Republican, who warned against the “Military-Industrial Complex”, which was influencing our foreign policy, and committing America to a constant overseas presence in foreign conflicts!
It is not even the party of Senator Barry Goldwater, the Republican Presidential nominee in 1964, who in later years warned against the growing influence in the party of the Religious Right with its insistence on promoting moral issues in politics, such as abortion and gay rights and school prayer, issues that Goldwater believed should not be part of American politics. For this, years after his losing campaign for President, he was vilified by the Christian conservatives!
The Republican party is no longer the party of Lincoln, Theodore Roosevelt, Eisenhower, or Goldwater! For those reasons, the party has lost its moorings, and many worry it is rapidly becoming marginalized, as it alienates the growing Hispanic and Latino population by its support of the Arizona illegal immigration law; as it campaigns to repeal health care; as it continues its battle against financial reform on Wall Street; and as it wages its refusal to support environmental legislation and energy alternatives–all issues that sum up the agenda of the future!