A rash of legal challenges to a core piece of US civil rights legislation is threatening the foundations of nearly half a century of laws to combat racial discrimination.

Republican-led state legislatures from Florida and Texas to Alaska have engineered a series of legal showdowns with the federal government over the 1965 Voting Rights Act that, following several court rulings last week, appear likely to end up before a US supreme court which has already hinted it is ready to revisit the heart of the law.

Civil rights activists warn that if the supreme court strikes down a key section of the Voting Rights Act, which gives the federal government some control over elections in states with a history of blocking African Americans from voting, then separate legislation affecting discrimination in other areas, such as in employment, education and housing, may also be vulnerable.

The moves against the Voting Rights Act also come as Texas and other states separately challenge the legality of racially-based affirmative action programmes in what some lawyers see as a concerted attempt to undermine and even kill off decades of civil rights legislation.

The legal assault has zeroed in on a provision of the Voting Rights Act which requires nine states – Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia – to seek approval from the US justice department in Washington for changes to voting laws or procedures. Some districts in seven other states are also bound by the legislation.

"There has been a proliferation of cases that aim to take down and rip out this core provision of the Voting Rights Act," said Debo Adegbile, acting president and lead counsel of the NAACP legal defence fund, who has argued in the defence of the law at the supreme court. "I think it's fair to say that the supreme court invited these challenges."

Several states have taken on the Obama administration over the law with legislation requiring people to produce photo identification to vote, redrawing electoral boundaries and measures limiting voter registration.

Obama's justice department has won a series of victories in recent weeks in which federal courts ruled that the changes amounted to racial discrimination and attempts to manipulate elections.

Last week, courts in Washington DC separately struck down plans by Texas to redraw constituency boundaries because they diminished the impact of a rapidly growing Latino vote and to require photo identification at the polls, which the court said would discourage minorities from voting.

The justice department has won similar victories over changes to election laws and procedures in other states, including Alabama and Florida, and is fighting legislation by South Carolina in a case the Obama administration appears likely to win.

But they may prove pyrrhic victories. Several state governments are looking to the conservative-leaning supreme court – which has already expressed its doubts about racially-based policy – to challenge the provision of the Voting Rights Act requiring "pre-clearance" by the US justice department, known as Section 5.

Nathaniel Persily, a Columbia University law professor whose work was cited in earlier supreme court opinion on the issue, said it is only a matter of time before the supreme court strikes at the heart of the Voting Rights Act by limiting the federal government's ability to enforce the legislation.

"The question is not whether Section 5 of the voting rights act will be struck down, but when and how. Will it die a death of a thousand cuts? Or will it be killed with one swift blow?" he said.

Persily said the supreme court hinted at its willingness to declare Section 5 unconstitutional in a 2009 ruling which upheld the Voting Rights Act while laying the seeds of its potential destruction.

In that case, officials in Austin, Texas said they should not have to ask Washington's permission to move a polling place from a house to a public school. The supreme court upheld the Voting Rights Act, which was extended for 25 years by large majorities in both houses of Congress in 2006.

But the chief justice, John Roberts, raised doubts about whether Section 5 could survive. He said the failure of Congress to update the law to take account of the changes it has brought about – such as black and white people voting in similar proportions across the south – raised questions about its constitutionality.

"The south has changed. The evil that Section 5 is meant to address may no longer be concentrated in the jurisdictions singled out for pre-clearance. The statute's coverage formula is based on data that is now more than 35 years old, and there is considerable evidence that it fails to account for current political conditions," Roberts wrote.

While flagging up his doubts, Roberts said that "the importance of the question does not justify our rushing to decide it" – a view widely read as encouraging further legal challenges to the law so the supreme court can consider the matter at length.

The chief justice's comments opened the floodgates. Since the 2009 ruling there have been more legal challenges to Section 5 than in the previous 44 years of its existence. Texas and Florida have already said they intend to ask to the supreme court to hear their cases. Two weeks ago, Alaska filed a constitutional challenge to its obligations under Section 5.

But the case closest to a hearing is out of an Alabama county, Shelby.

The county's legal bills are being paid by the Project on Fair Representation, which describes itself as a legal defence fund fighting "the creation of racially gerrymandered voting districts". Its director, Edward Blum, says that Section 5 exceeds Congress's powers under the constitution and that it punishing states for past sins.

"Section 5 was a draconian yet completely necessary provision in 1965 when mostly southern jurisdictions we purposely shutting out blacks from the ballot box. Today, however, Section 5 is no longer a needed remedy and has evolved into a racial gerrymandering tool," he said. "African Americans and Hispanics no longer live in barrios and ghettos. Over the last 40 years, inner city America, which was heavily minority, has emptied out and African Americans and Hispanics live in all corners of these large major metropolitan areas now."

But Adegbile said that the proliferation of laws being blocked by the justice department and courts under Section 5 is evidence of continued need for the Voting Rights Act.

"Courts with judges appointed by Republican presidents and Democratic presidents are saying these underlying voting changes are discriminatory and will harm minority voters," he said. "What we see is a rash of voting measures targeted at minority voters in a number of places across the country that surprises folks who believed we had moved beyond though practices. I think the average person understands that it seems there's still different ways that you can try to win elections. One is by mobilising your voters. The other is by blocking a certain segment of the electorate and that second approach remains, unfortunately, a technique that is being deployed in too many places around the country."

The supreme court has also taken up another case, involving race based affirmative action, that potentially has a profound impact on civil rights. Abigail Fisher sued after she was denied a place at the University of Texas claiming that she was discriminated against because she is white.

In 2003, a divided supreme court ruled that a student's race could be considered in order to achieve a diverse university student body, but only after attempting to use other means. Fisher argues that Texas law already provides for a diverse admissions policy and therefore race based affirmative action was unnecessary.

The Project on Fair Representation is financially backing that legal challenge, too. Blum said that he regards affirmative action based on race as a mistake from the beginning. "Affirmative action assumed that all African Americans regardless of their family income or their family educational background were deserving of some special help," he said.

Persily said that if that central part of the Voting Rights Act is struck down then other civil rights legislation is likely to come under legal attack.

"The thing about Section 5 of the voting rights act is that it's been the standard against which all other exercises of federal power in the civil rights realm have been judged. When you're talking about the disabilities act or the age discrimination in employment act or any number of other pieces of legislation, when the courts find problems with those laws they say they're not as good as the voting rights act," he said.

"So now the gold standard for civil rights legislation is potentially going to be declared unconstitutional with unclear repercussions for all kinds of other laws."

Adegbile agrees. "If the rulings were overly broad, the knock-on effect could be felt in other areas such as employment, education and the like. I think that there are serious threats," he said.

Blum hopes so, saying that he believes employment laws and public contracting, in which a proportion of government contracts are awarded to minority-owned firms, will be particularly vulnerable to legal challenge.

For Adegbile, the looming supreme court battles are a test of where the US stands on civil rights half a century after the laws that changed America.

"Right now we are at a moment where there are competing visions of equality and opportunity in America. One side says that we have to celebrate our progress but recognise that we can do better. The other view is that we should stop talking about our history. We should deny the context, and we should move past all of this as if to pretend that racial discrimination does not continue to exist in America."